coral

Abstract

Animals often occupy home ranges where they conduct daily activities. In many parrotfishes, large terminal phase (TP) males defend their diurnal (i.e., daytime) home ranges as intraspecific territories occupied by harems of initial phase (IP) females. However, we know relatively little about the exclusivity and spatial stability of these territories. We investigated diurnal home range behavior in several TPs and IPs of five common Caribbean parrotfish species on the fringing coral reefs of Bonaire, Caribbean Netherlands. We computed parrotfish home ranges to investigate differences in space use and then quantified spatial overlap of home ranges between spatially co-occurring TPs to investigate exclusivity. We also quantified the spatial overlap of home ranges estimated from repeat tracks of a few TPs to investigate their spatial stability. We then discussed these results in the context of parrotfish social behavior. Home range sizes differed significantly among species. Spatial overlap between home ranges was lower for intraspecific than interspecific pairs of TPs. Focal TPs frequently engaged in agonistic interactions with intraspecific parrotfish and interacted longest with intraspecific TP parrotfish. This behavior suggests that exclusionary agonistic interactions may contribute to the observed patterns of low spatial overlap between home ranges. The spatial overlap of home ranges estimated from repeated tracks of several TPs of three study species was high, suggesting that home ranges were spatially stable for at least 1 month. Taken together, our results provide strong evidence that daytime parrotfish space use is constrained within fixed intraspecific territories in which territory holders have nearly exclusive access to resources. Grazing by parrotfishes maintains benthic reef substrates in early successional states that are conducive to coral larval settlement and recruitment. Behavioral constraints on parrotfish space use may drive spatial heterogeneity in grazing pressure and affect local patterns of benthic community assembly. A thorough understanding of the spatial ecology of parrotfishes is, therefore, necessary to elucidate their functional roles on coral reefs.

Abstract

This project uses geospatial data to generate custom polygons in an interactive setting to represent the size and location of coral reefs to extract insights from coral reef-centered data sets. Historically, the data used by the Reef Restoration Group Bonaire exists in disparate sources, making it difficult to track and analyze the outcomes of their restoration work. Additionally, this information is not available in a digestible format for other audiences who would be interested in this data, such as citizen scientists seeking coral reef health statistics, the general public wanting to better understand the coral reefs surrounding Bonaire or recreational scuba divers interested in learning more about potential dive sites. Numerous data points were extracted for each reef in scope, largely from two data sources to highlight the efforts of the Reef Restoration Group Bonaire and biodiversity of each reef. These data elements were visualized using Tableau, an interactive data visualization software, which provided the vehicle for the exploration and interaction with the data. The development of the custom Tableau interface and geospatial polygons representing the coral reefs, allowed for an interactive user experience for exploration and analysis of the health and biodiversity of each reef by plotting these polygons on a world map. The outcome gave the precise location and size for each reef allowing for the identification of reef boundaries using latitude and longitude coordinates as the polygon vertices. These outcomes indicate there is a tangible benefit possible by representing geospatial data in an interactive environment for data analysis and extraction of insights.

Abstract.

Much research is being conducted on environmental issues but more knowledge does not necessarily lead to more decisions that take into account such knowledge. A low research uptake can therefore be a threat to ecosystems. An example is research going on about coral reefs and pollution in Curaçao. Coral reefs are vibrant ecosystems and provide many services. They support the economy and protect the coasts. However, they are declining as many hazards threaten them such as sewage that pours out into the sea. Scientific research is being conducted on that topic, but a major issue is the insufficient uptake of research by the policy sphere and the civil society to adopt environmental friendly decisions and behaviours. This master thesis is embedded in the SEALINK project, which aims at understanding how pollution such as sewage impacts the coral reef in Curaçao, and more precisely to its work package on research uptake strategies. This thesis first identifies in the literature the conditions under which research uptake is optimal. Literature highlights three criteria that knowledge should meet in order to have an optimal research uptake: legitimacy, credibility and salience. The salience of the scientific knowledge produced on sewage pollution and its impact on the reef is the focus of this thesis as the legitimacy and credibility of the knowledge produced on sewage are assumed to be met already. Salience refers to the relevance of the knowledge produced for the users of science, such as policy makers. A lack of salience can be the cause of differences in timerames, in the vocabulary used between the scientist and users of knowledge, for instance. The stakeholders that affect sewage in Curaçao, such as the ministry in charge of sewage management, companies that pick up sewage, the tourism industry, or fishermen, were then listed to be interviewed. Interviews of these stakeholders were conducted to explore the behaviours undermining salience of the knowledge produced on the topic at hand. The results show that this knowledge lacks salience because of an operational misfit between the demand for, and supply of knowledge. Recommendations to the local actors and to future researchers on solutions to create more salient knowledge and therefore to have optimal research uptake to protect the reef better, are proposed under the form of science-policy interfaces with an emphasis on knowledge co-production as the main approach to improve the science and practice relationship.  

Part of the larger The impacts of climate change on Bonaire (2022-present) report available here.
 

Summary

Coastal hazards pose a significant threat to small islands, especially in combination with Sea Level Rise (SLR). Currently, the small Caribbean island of Bonaire is poorly protected against coastal flooding and there is a lack of local knowledge on potential adaptation options and their benefits and trade-offs. This study aims to fill this gap by evaluating how different coastal adaptation options to protect Bonaire are valued, considering economic, social, environmental, and technical criteria. This is evaluated using a participatory Multi-Criteria Analysis (MCA) that includes key stakeholders through semistructured interviews and the use of an online questionnaire. A wide variety of coastal adaptation options, ranging from grey infrastructure to softer Nature-based Solutions (NbS), is assessed based on an interdisciplinary set of 10 different criteria, providing a holistic view of the consequences of each option. The results show that NbS, especially mangrove restoration, and spatial zoning measures are overall perceived to be most beneficial. The least favourable adaptation strategies include the construction of any type of seawall and doing nothing. While an MCA does not lead to a final perfect solution, it does provide valuable comparative information about potential future adaptation strategies for Bonaire, which can be used to aid policy makers in the decision-making process. Moving forward, it is important to further strengthen the results of this study by conducting additional quantified analyses, including an evaluation of the spatial suitability of specific measures or combinations of measures. Moreover, to ensure public support for any final policy decisions, regardless of the specific measures that a

Part of the larger The impacts of climate change on Bonaire (2022-present) report available here 

Summary

This paper studies the macroeconomic consequences of climate-induced reef degradation for Bonaire. Bonaire’s coral reefs progressively face the unavoidable reality of climate change, with its effects increasing in severity. Degradation of the island’s reef ecosystems may affect annual tourism arrivals as the reefs form one of the main attractions for visitors to Bonaire. Consequently, the industries that rely on tourist expenditures will suffer and thus the local economy. Coral reef-based tourism creates a unique opportunity to investigate the impacts of global warming on the macroeconomic performance of Bonaire. This paper employs the emission scenarios SSP1-1.9, SSP2-4.5, SSP3-7.0, and SSP5-8.5 of the AR6 IPCC 2021 to study the effects of coral reef degradation on the social carrying capacity of the coral reefs. Subsequently, the potential effects of reduced dive tourism and the induced effects of a change in tourism demand are translated into changes in sectoral outputs by employing input-output analysis. Coral reef degradation is expected under all scenarios, except the SSP1-1.9 scenario where a slight recovery of coral reefs is possible.

This study finds a contraction in GDP between 25 USDm and 173 USDm by 2050 (between 2 to 18 percent of GDP in 2050), depending on the applied climate scenario. Moreover, a tourism income multiplier of 0.85x is found, which indicates a strong interlinkage between tourism income and the local economy, as from every dollar of tourism income 85% enters the local economy. This indicates that any losses in tourism demand will significantly result in macroeconomic damages for Bonaire. It can thus be expected that climate change will have a substantial impact on coral reefs as a vital tourism asset on Bonaire, with more extreme emission scenarios leading to stronger negative effects on the local economy.

Summary

Coral reefs are a vital part of Curaçao’s economy, providing revenue from ecotourism and fisheries, as well as providing shoreline protection. A vital coral species, Diploria strigosa, is a major reef-building species around the island, and contributes enormously to the health of the reefs, making it a prime candidate for this project. Physical oceanic processes, such as waves and currents, influence the health of these corals by introducing oxygen-rich water through mixing of the water column. In order to understand more about the growth and vitality of coral around Curaçao, it is therefore critical to understand how these processes influence the movement of oxygen around coral reefs.

This thesis set out to collect field data to investigate the existence of a relationship between hydrodynamics and dissolved oxygen near coral reefs around the island of Curaçao, as part of a larger project, the SEALINK project. SEALINK, part of the Dutch Research Council (NWO)’s Caribbean Research program, is an interdisciplinary research initiative to assess the impact of land-based and water-borne substances on the coral reefs of the Dutch Caribbean. Through a fieldwork campaign, dissolved oxygen concentration, wave data, and current velocity data was collected from seven study sites on the southern coast of Curaçao. Acoustic Doppler current profilers (AD2CP) and oxygen loggers were deployed through diving, and left on the seafloor to measure for six hours. A statistical analysis was run to test the validity of using current velocities as a predictor for dissolved oxygen values. Finally, a computational fluid dynamics (CFD) model was created using the fieldwork data in order to assist in the understanding of processes that influence dissolved oxygen around coral reefs. The results from fieldwork show that the extent of the relationship between waves, currents, and dissolved oxygen depends greatly on the location and tidal cycle. Study sites closer to the eastern point of the island showed that velocity and dissolved oxygen are connected, and that velocity has a greater capacity to predict dissolved oxygen values. The CFD model assists in a deeper comprehension of the influence of flow and other processes that can impact dissolved oxygen fluctuations around coral reefs.

Abstract

Background: The importance of symbiosis has long been recognized on coral reefs, where the photosynthetic dinof lagellates of corals (Symbiodiniaceae) are the primary symbiont. Numerous studies have now shown that a diverse assemblage of prokaryotes also make-up part of the microbiome of corals. A subset of these prokaryotes is capable of f ixing nitrogen, known as diazotrophs, and is also present in the microbiome of scleractinian corals where they have been shown to supplement the holobiont nitrogen budget. Here, an analysis of the microbiomes of 16 coral species collected from Australia, Curaçao, and Hawai’i using three different marker genes (16S rRNA, nifH, and ITS2) is presented. These data were used to examine the effects of biogeography, coral traits, and ecological life history characteristics on the composition and diversity of the microbiome in corals and their diazotrophic communities.

Results: The prokaryotic microbiome community composition (i.e., beta diversity) based on the 16S rRNA gene varied between sites and ecological life history characteristics, but coral morphology was the most significant factor affecting the microbiome of the corals studied. For 15 of the corals studied, only two species Pocillopora acuta and Seriotopora hystrix, both brooders, showed a weak relationship between the 16S rRNA gene community structure and the diazotrophic members of the microbiome using the nifH marker gene, suggesting that many corals support a microbiome with diazotrophic capabilities. The order Rhizobiales, a taxon that contains primarily diazotrophs, are common members of the coral microbiome and were eight times greater in relative abundances in Hawai’i compared to corals from either Curacao or Australia. However, for the diazotrophic component of the coral microbiome, only host species significantly influenced the composition and diversity of the community.

Conclusions: The roles and interactions between members of the coral holobiont are still not well understood, especially critical functions provided by the coral microbiome (e.g., nitrogen fixation), and the variation of these functions across species. The findings presented here show the significant effect of morphology, a coral “super trait,” on the overall community structure of the microbiome in corals and that there is a strong association of the diazotrophic community within the microbiome of corals. However, the underlying coral traits linking the effects of host species on diazotrophic communities remain unknown.

Using cryopreserved reproductive cells of elkhorn corals, researchers have crossbreed individuals from Florida and Puerto Rico with those of Curaçao in an important first step to creating more heat tolerant populations. The goal is to increase genetic diversity within at-risk populations of corals to help build resilience for future generations.

Genetic evolution allows entire populations to adapt, over many generations, to their local environments. However, environmental conditions are now changing at an accelerated rate, and in some cases, outpacing the ability of species to adapt. This is where Assisted Gene Flow (AGF) comes into play; this conservation intervention involves directly introducing genetic diversity into at-risk populations. In other words, researchers can now influence the reproductive process of threatened species in order to introduce new genetic diversity and thus facilitate faster evolution.

Elkhorn coral. Photo credit: Hans Leijnse

Elkhorn Coral

Corals are excellent candidates for the Assisted Gene Flow technique, especially the IUCN “critically endangered” elkhorn coral (Acropora palmata). Estimates place the decline in their populations around 95% since the 1980s. Further, they’ve struggled to keep up with changing water conditions and have documented reproductive issues. Mature corals are difficult to relocate for the purposes of AGF and coral gametes (reproductive cells) lose viability within a few hours. Researchers have therefore used cryopreservation to achieve AGF in this species.

Within the region, there are two distinct populations of elkhorn coral, one from the northwestern Atlantic and one from the Caribbean. A central, mixed zone exists near Puerto Rico. Over time, these populations have evolved to their unique thermal and oceanographic environments.

New Techniques

A recently published report highlighted the successful demonstration of using AGF to fertilize elkhorn corals. This research was a collaborative effort by CARMABI, Smithsonian Conservation Biology Institute, Penn State University, Florida Aquarium Center for Conservation, and Mote Marine Laboratory. Using cryopreserved sperm from eastern and central Caribbean (Florida and Puerto Rico) elkhorn corals, researchers were able to fertilize eggs from western Caribbean (Curaçao). By mixing these genetic pools, researchers may be able to accelerate region-wide adaptations to climate change.

Elkhorn coral. Photo credit: Duncan MacRae

Future of Conservation

In addition to achieving the highest ever survival rate for elkhorn coral juveniles, these researchers were able to generate the largest living wildlife population ever created from cryopreserved cells. This research proved the viability of using cryopreserved genetic material to increase genetic diversity. The future of coral conservation will require innovative techniques, such as AGF, to help keep pace with the accelerated changed due to climate change. By identifying and cryopreserving genetic material for threatened corals, crossbreeding with more tolerant populations may be the key to preserving these species in the future.

To read the full report, please use the DCBD link below.

https://www.dcbd.nl/document/assisted-gene-flow-using-cryopreserved-sper...

Article published in BioNews 48

Researchers from University of Amsterdam and CARMBABI Foundation implemented 3-dimensional reef surveying techniques to improve representation of species found within hidden cavities previously overlooked by 2D methods. 12 sites along the coast of Curacao were selected and analyzed. Improved surveying techniques will increase overall understanding of the complexities of these vital ecosystems.

Photo Source: Niklas Kornder

Coral reefs are one of the most diverse ecosystems on the planet.  Coral’s beautiful skeletal structure plays an important role in providing reef habitat, nursery and hunting ground while also protecting coastal zones.  Climate change continues to be a significant threat to these areas, making the need for accurate mapping and surveying techniques vital to researchers’ ability to detect change. Traditional mapping techniques use a 2D approach to project surface cover estimates throughout a 3D structure.  Unfortunately, this technique misses hidden habitats, such as overhangs and cavities, which can result in an under representation of biomass estimates.

Photo Source: Eric Mijts

2D versus 3D

New research from the University of Amsterdam and CARMBABI Foundation compared 2D versus 3D survey techniques. Traditionally, organism abundance was calculated as the percentage of projected reef cover.  Previously, this was done by 2D surveys, however a new strategy hopes to improve on this technique through the combination of photograph analysis, diving surveys and computer modeling. Researchers surveyed 12 coral areas on the island of Curacao, then compared 3D benthic community estimates against traditional 2D projected surface cover analysis.

The Results

During this research, scientists found that while using 2D techniques, the relative contribution of organisms which grow vertically (gorgonians and massive sponges) was up to two times and 11 times lower, respectfully, than their contribution to reef biomass.  In addition, hidden areas represented nearly half of all total reef substrate, meaning two thirds of all coralline algae and almost all encrusting sponges are not included within traditional surveying techniques.

Using a variety of different metrics, this research presents adjustments to current monitoring techniques, highlighting the importance of evaluating the ecological contributions of previously disregarded or underrepresented species.  These metric conversions can be used to complement traditional survey techniques to provide improved estimates for biovolume, biomass and element composition (stocks of organic carbon and nitrogen) within coral reef communities.

Implications

Photo source: Francesco Ungar

Understanding the true composition of coral reefs is vital for designing and implementing effective conservation strategies. Coral’s unique ability to create complex habitats is vital to maintaining high community diversity and abundance in shallow water environments.  It is estimated that nearly 75-90% of coral reef ecosystems are hidden under the surface skeleton.  This means that for every m2 that can be seen, there is up to 8m2 of additional habitat underneath. This study suggests that 2D approaches may be useful to produce relatively fast estimates of reef ‘health’ but a 3D approach is needed to understand coral reef’s true composition.

https://www.dcbd.nl/document/implications-2d-versus-3d-surveys-measure-a...

Article published in BioNews 47

A recent report released by STINAPA notes the occurrence of coral bleaching on Bonaire between 2016 and 2020.  During this study, coral bleaching was detected every year, highlighting the need for continuous monitoring and rigorous conservation measures to build resilience moving forward.

The beautiful corals of Bonaire are loved for their stunning array of colors, but what many don’t realize is that these colors are not from the coral themselves, but small microscopic alga, referred to as zooxanthellae or symbiodinium, living within them.  This alga and coral have a symbiotic relationship, where the zooxanthellae provide nutrients to the coral in exchange for protection and habitat within the coral’s skeletal structure.  Under normal conditions, this relationship is mutually beneficially, however, if the zooxanthellae become toxic, the coral can evict their partner, leaving behind its colorless abode.

Photo credit: Kai Wulf

Climate  Change

One of the many negative effects of climate change is a slow but steady increase in average Sea Surface Temperatures (SST).  While the exact causes and mechanisms of coral bleaching are still being investigated, one theory that has strong support hypothesizes that bleaching is triggered by the production of excessive abnormal oxygen molecules.  As SSTs rise above normal (even if just for just a few weeks), the zooxanthellae are unable to effectively photosynthesize and begin to produce reactive oxygen which can damage coral tissue.  As a defensive response, the coral sometimes ejects the alga, leaving its white skeletal structure empty giving it the appearance of being “bleached”.

If enough corals eject enough zooxanthellae, this becomes known as a mass coral bleaching event. These events can last anywhere from days to months and, in extreme events, even years. Unfortunately, the coupling of worsening water conditions due to human activity (pollution, overfishing and uncontrolled land development) and stressors due to climate change have led to an increase in the frequency and duration of mass coral bleaching events.  Without the zooxanthellae producing energy, corals are forced to rely on stored energy reserves and feeding directly on zooplankton. Bleaching events can be dangerous for corals even if they do not result in direct mortality as this can leave them more susceptible to disease, decreases coral spawning success and can lead to long term changes within the community composition.

Photo credit: Kai Wulf

Building Resilience

Luckily, not all coral, or zooxanthellae, are the same. In fact, new research has uncovered differences between corals which host a single type of zooxanthellae versus those with a more diverse array, where some may be more tolerable to temperature shifts than others.  A new theory, known as the Adaptive Bleaching Hypotheses, even states that following bleaching events, the make up of zooxanthellae may shift within corals, allowing new, more resilient combinations of zooxanthellae to move in. This creates the opportunity for coral communities to build resilience after particularly destructive years.

Bonaire

Although global bleaching events have been happening regularly since the late 1990s, Bonaire suffered its first significant coral lost due to bleaching in 2010.  During this episode, Bonaire registered nearly 10% coral mortality among populations at 10m depth.  Since 2016, some degree of coral damage, ranging from paling to full bleaching, has occurred on Bonaire’s reefs every year.  Already, even without the official survey for 2021 being completed, divers have reported bleaching at depths of 35m and deeper.

A new report, published by STINAPA, highlights the impact coral bleaching has had within the Bonaire National Marine Park between 2016 and 2020.  Each year, after SST began to drop (usually between November and December), STINAPA surveys ten sites within the park, noting signs of bleaching. These sites included eight locations along the leeward side of the island and two off the coast of Klein Bonaire, Figure 1.  At each location, quadrants were photographed at depths of 10 and 25m, with additional photographs taken at 5m for four sites starting in 2017.

Trouble in the Deep

Over this four-year study, coral bleaching was detected within the photographed quadrants every year, affecting 26% of corals in 2016, 55% in 2017, 9% in 2018, 24% in 2019 and 61% in 2020.  It should be noted that methodology changes in 2018 may have contributed to an underrepresentation of coral bleaching.

STINAPA found that the corals most susceptible to bleaching are those found at deeper depths. Interestingly, when comparing the three depths, there were significant bleaching differences between 25 and 10m, but no significant differences between 10 and 5m.

STINAPA also found that bleaching trends from 2020 indicate that certain species of coral are at higher risk of bleaching than others.  For example, corals such as Orbicella and Agaricia (Boulder, Mountainous star and Lettuce corals) were more often bleached, yet Madracis species (Yellow pencil and Ten-rayed star corals) appear to be more resilient.

Map of the 10 coral bleaching survey sites on the leeward coast of Bonaire and Klein Bonaire. (STINAPA, 2021)

The Future

Protecting these corals will require action at all levels.  Locally, the government can help build resilience through more effective fishery management, wastewater treatment and promote responsible coastal development and sustainable tourism.  Individually we can all help by minimizing our contribution to pollution, avoiding direct contact with the reef while swimming or diving and wearing reef safe sunscreens in the water.

Together, by promoting a nature first attitude towards conservation, we can help build stronger more resilient environments to combat the threats of climate change moving forward.

https://www.dcbd.nl/document/coral-bleaching-bonaire-national-marine-par...

Article published in BioNews 44